In the field of signal transmission, often there is need to transmit a signal or energy from a circuit of one voltage domain to a circuit of another voltage domain, or from one medium to another medium. Due to the difference in voltage domain or medium, the signal may interfere with or cause breakdown in the peripheral circuits by the parasitic path during the transmission and result in damage. Considering the reliability of the circuits, electrical isolators, couplers, or isolation barriers are usually adopted for transmitting signals between the circuits of different voltage domains, so as to protect the circuits.
Electrical isolators are applicable to many fields of power supply circuits, such as power supply systems (e.g., power supplies, motor control systems, server power supply systems, and home appliances), illumination control systems (e.g., LED controllers), industrial motor systems (e.g., robotic arms and car motors), and so on. The aforementioned power supply circuit systems usually generate signals or orders through a control circuit, so as to control the output stage circuit and transmit the energy to the load.
Currently, electrical isolators are usually implemented by using optical couplers, capacitors, or transformers. In the case of using an optical coupler as the electrical isolator, the manufacturing process of LED is not compatible with the transistor manufacturing process (e.g., CMOS manufacturing process) and LED has issues such as light decay and heat loss. Therefore, LED cannot be integrated into the chip and additional packaging is required. Nevertheless, if a transformer or capacitor, which can be integrated into the chip, is used as the electrical isolator, transmission of high frequency signals may be needed in order to achieve efficient transmission. As a result, the circuit equipped with such an electrical isolator will require additional modulation and demodulation functions for signal transmission. Thus, how to implement an electrical isolator that can lower power consumption and reduce signal distortion remains an issue that needs to be addressed.